1. Field of the Invention
This invention relates to a rotor of a generator for an internal combustion engine, and a method for manufacturing the same. More particularly, the invention relates to a synthetic resin molded rotor with a core, which is made of a plurality of magnetic steel plates laminated together and is provided with a magnet, and the manufacturing method thereof.
2. Description of Related Art
A recoil starter has been used for cranking or starting a small internal combustion engine. In the recoil starter, an engaging portion of a reel engages a pawl of a rotor for rotating the rotor when a rope wound on the reel is pulled by hand. A crank shaft of the engine is rotated by the rotor to cause cranking or starting the engine, because the rotor is connected to a top end of the crank shaft.
As a result, magnetic flux ejected from a magnet in the rotor interlinks with a generator coil which is immovably fixed to the engine. Therefore, the coil generates electric power, which is used for sparking an ignition plug of the engine, so that the engine is started.
The rotor of the starter, therefore, requires the pawl at the rotor, which transmits rotation of the reel rotated by the rope to the rotor. In this respect, rotation of the rotor should not be transmitted to the reel. Further, when rotational speed of the engine becomes high, the pawl should move to a peripheral side of the rotor by centrifugal force.
In order to accomplish the above mentioned operations or functions of the pawl, the pawl is rotatably supported on a support shaft mounted on the rotor.
In the conventional starter, a support shaft is fitted into a through hole of a rotor and is fixed by an engaging ring. Accordingly, a structure for mounting the pawl is complex, and number of parts and steps for manufacturing the rotor are required.
Also, in a conventional molded rotor, a synthetic resin is molded onto a core made of a plurality of magnetic plates laminated with each other. The laminated magnetic plates should be connected to each other, and also the plates should be connected to a boss of the rotor by rivets. Since the laminated plates should be connected together before molding with resin, it requires some additional manufacturing steps.
Further, in the conventional molded rotor with a laminated core, a metal boss must be connected to the center of the core. A conical opening must be formed at the center of the metal boss for connecting the rotor to a top tapered end of a crank shaft of an engine. Therefore, the boss must be separately formed, which requires additional parts and assembly steps. Also, the metal boss increases weight of the rotor, which contradicts object of lightening the rotor.
In order to solve the above problems, it was tried to form a conical opening directly on the center of the laminated core by lathe. However, this was not successful, because the laminated steel plates becomes disassembled at the center of the core. Further, the rotor could not be firmly connected to the top end of the crank shaft, because the steel plates deform.